Gas turbine engines typically include several rotor discs which carry a plurality of rotor blades extending radially outwardly into the hot working medium gases which makes it usually necessary to provide cooling to the blades. To remove heat from the rotor blades, cooling air is tapped from the engine's compressor and directed into passages within the disc and blade interiors. The cross-section of the passages is typically circular, since this is the cheapest and easiest to produce. During operation, rotational forces induce tangential stress in the disc material where the openings of the cooling air passages are subject to major hoop stresses with a high risk of crack initiation.
EP 0 814 233 B1 describes a gas turbine engine rotor disc with radially extending cooling air supply passages, each passage having a cross-sectional configuration which renders the ends of passages less likely to act as site of hoop-stress induced cracks.
U.S. Pat. No. 4,344,738 describes a gas turbine engine rotor disc with cooling air holes where the elongated axis of each cooling air hole lies in a plane perpendicular to the axis of symmetry of the disc to reduce tangential stress concentration factors.
U.S. Pat. No. 4,522,562 describes the cooling of turbine rotors where the disc is equipped with two sets of channels bored respectively close to each of the sides of the disc and in conformity with its profile in which the cooling air of the turbine blades flows in order to cool the disc.